Problem: Simplify the following expression: $z = \dfrac{7a}{2} + \dfrac{-5a}{2}$
Solution: Since the expressions have the same denominator we simply combine the numerators: $z = \dfrac{7a - 5a}{2}$ Combine like terms: $z = \dfrac{2a}{2}$ Simplify by dividing numerator and denominator by 2: $z = \dfrac{a}{1}$ $z = a$